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Ohmic Contacts to GaAs

IP.com Disclosure Number: IPCOM000049997D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Heiblum, M: AUTHOR [+3]

Abstract

In a thermal annealing process, contact resistivity drops when the density of Ge-Ni rich clusters in a AuGeNi contact increases. The cooling rate after annealing provides a further improvement.

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Ohmic Contacts to GaAs

In a thermal annealing process, contact resistivity drops when the density of Ge-Ni rich clusters in a AuGeNi contact increases. The cooling rate after annealing provides a further improvement.

Laser annealing provides a very fast process which produces smooth surfaces and low contact resistivity. The process is surface dependent and will cause annealing of only the ohmic contacts without affecting the GaAs surface. An additional advantage of using a CO(2) laser is that it heats the contact from above and thus accentuates the cooling from the substrate, thereby providing a thicker and more uniform n+ region under the contact, and leads to lower contact resistivity.

A CO(2) radiation of 9.3 micrometers has a strong absorption coefficient in SiO(2). The metallurgy is NiAuGe-SiO(2), in this order, where the SiO(2) helps to maintain good surface morphology during the annealing process and serves as the 9.3 micrometer absorber, while the GaAs material is transparent at this wavelength. The SiO(2) is heated by the laser pulse and causes melting of the underlying contact. Recrystallization occurs on cooling. Beam size is not of major concern, since the part of the beam which hits the GaAs not covered with SiO(2) passes through without heating. This is a major advantage over laser annealing with visible wavelengths.

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